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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    /**
     * unshift(被添加元素) push（被添加元素）
    */
    var currentDay = "星期四";
    var daylist = [currentDay];
    daylist.unshift("星期一","星期二","星期三");
    daylist.push("星期五","星期六","星期天");
    console.log(daylist);

    var arr1 = ["hello","world"];
    var arr2 = ["hello","javascript"];
    var arr3 = ["arr3"];
    /**
     * arr.concat(arr1,arr2);
     * 会将arr1和arr2合并得到一个新数组
     * 但不会对arr产生影响
    */
    var arr4 = arr1.concat(arr2);
    console.log(arr4);

</script>
</html>